As discussed in more detail in a previous U.S. Pat. No. 4,117,846, incorporated herein by reference, electrosurgery is the use of high frequency electrical current for cutting tissues and also for causing a coagulation of hemostasis of tissues. The basic mechanisms responsible for either the cutting or coagulation of the tissues is the production of heat either at the immediate site of the electrical arc or in adjacent tissues. If the electrode is small, the heating will be concentrated near the electrode's point of contact with a patient. Obviously, this is desired with an active electrode which is used to cause the cutting or coagulation of the patient. However, no tissue heating is desired near the point where the current leaves the patient at a return electrode or grounding pad electrode. Thus, the ground pad electrode should provide a low impedance and a low current density path for the return current. If the grounding pad does not provide good patient contact, burns can occur. Therefore, an adequate grounding pad which conforms to the patient and resists patient scretching is necessary in order to assure safe, burn-free electrosurgery.
There are numerous electrodes in the prior art, including those which were disclosed in the prior patent. In that patent, an electrode assembly is disclosed which has a series of projections around the periphery of a main electrode body. When this electrode assembly is placed on the patient, the adhesive pad makes contact with the patient around and within the recesses between the projections to provide good contact between the gel pad under the electrode and the patient's skin. It has also been disclosed in German Pat. No. 2,239,596 to Hetz to provide small recesses in a bare electrode so that the overlying adhesive tape fills these recesses and sticks to the skin of the patient. Small openings in a rubber-backed bare electrode have also been disclosed in U.S. Pat. No. 1,973,387 to Neymann et al, the number of openings being varied to increase or decrease the conductive area of the electrode.
While the '846 U.S. patent provides good contact for an elongate gel pad and electrode, the main body of the gel pad is still subject to some loose contact, as are the gel pads of other prior art patents.